Semiconductor device having a through electrode with a low resistance and method of manufacturing the same

ABSTRACT

A method of manufacturing a through electrode. While using at least a first conductive film for a gate electrode as a mask, an inner trench and a peripheral trench is formed. The Inner trench is provided for an inner through electrode having a columnar semiconductor. The peripheral trench is provided for a peripheral through electrode around an annular semiconductor surrounding the inner trench. The inner trench and the peripheral trench are filled with a through electrode insulation film and a through electrode conductive film, respectively, to form an inner through electrode and a peripheral through electrode.

This application claims priority to prior Japanese patent application JP2005-357819, the disclosure of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor device, and moreparticularly to a semiconductor device having a through electrode whichforms a three-dimensional semiconductor device, and to a method ofmanufacturing such a semiconductor device.

Three-dimensional semiconductor devices having a plurality of stackedsemiconductor devices have been proposed in recent years. In thesethree-dimensional semiconductor devices, the respective semiconductordevices are electrically connected to each other by through electrodes,which extend through semiconductor substrates.

FIGS. 1 and 2 show a conventional three-dimensional semiconductordevice. The three-dimensional semiconductor device shown in FIG. 1 hasthree semiconductor devices 3, 4, and 5 and a support substrate 1 onwhich the semiconductor devices 3, 4, and 5 are mounted. Eachsemiconductor device has a through electrode 7 extending through asemiconductor substrate. The semiconductor devices are connected to eachother by bumps 6, which are connected to the through electrodes 7, andalso connected to a wiring pattern 2 on the support substrate 1. FIG. 2is a cross-sectional view of one through electrode 7. The illustratedthrough electrode 7 is produced after completion of a wiring process ina semiconductor fabrication process.

An opening is formed in an insulation film 17 in a state in whichinterconnections 16 are formed in the semiconductor device. A trench isformed in the semiconductor substrate 11. A through electrode insulationfilm 7 b is deposited on an inner wall of the trench. Further, thetrench is filled with a through electrode conductive film 7 a. Then, anupper surface of the through electrode conductive film 7 a is flattenedby CMP or the like so as to have the same height as a surface of thesemiconductor. A rear face of the semiconductor substrate 11 is groundso that the semiconductor substrate 11 has a predetermined thickness. Arear insulation film 18 is deposited on the rear face of thesemiconductor substrate 11. Then, an opening is formed in the rearinsulation film 18, and a bump 19 is formed in the opening. A bump 19may be formed on the front face of the semiconductor substrate asneeded. If no bump is formed on the semiconductor substrate, aprotective insulation film is formed on the semiconductor substrate.

These through electrodes are used as power source lines and signallines. Accordingly, It is desirable that the through electrodes have alow wiring resistance and a small stray capacitance. Through electrodeshaving a high wiring resistance cause reduction of a voltage and delayof signals to thereby lower an operating speed. Finally, thesemiconductor may not work. Further, if through electrodes have a largecapacity, a signal waveform is disturbed by delay of signals and noisebetween signals, so that high-speed data transfer cannot be performed.Accordingly, in order to reduce a resistance of a through electrode, itis necessary to increase a diameter of a trench formed in asemiconductor substrate and fill the trench with a conductive film.Further, in order to reduce a capacity of a through electrode, it isnecessary to thicken an insulation film between a semiconductorsubstrate and a conductive film and to use an insulation film having asmall dielectric constant. However, only limited types of insulationfilms can be used in a semiconductor fabrication process. As a result,it is necessary to increase a film thickness of an insulation film.

Accordingly, in order to produce a through electrode, a trench having adiameter of several tens of micrometers should be formed in asemiconductor substrate, and a through electrode insulation film 7 bshould be deposited as thick as several micrometers to several tens ofmicrometers. In the prior art, when a conductive film or an insulationfilm having a film thickness in the above range, deposition should beperformed for a long period of time. Thus, a heavy load is imposed on amanufacturing process. Further, in a case of deposition of a conductivefilm having a thickness of several tens of micrometers, the depositedgrain becomes non-uniform as the film thickness becomes larger. Thenon-uniform grain causes variation of properties of the conductive filmso as to increase a resistivity of the conductive film. Thus, it hasbeen desired to develop a structure of a through electrode having a lowresistance and a small capacity, and to establish a method ofmanufacturing such a through electrode.

Japanese laid-open patent publications Nos. 2003-017558 and 2002-289623relate to through electrodes. Japanese laid-open patent publication No.2003-017558 discloses forming a trench having a diameter of several tensof micrometers in a semiconductor substrate, then filling the trenchwith an application insulation film, etching the semiconductor substrateto form a trench in the semiconductor substrate, and depositing aconductive film in the trench to produce a through electrode with theconductive film having no cavities. Japanese laid-open patentpublication No. 2002-289623 discloses a second insulation area providedoutside of a through electrode to prevent short-circuits between thethrough electrode and a semiconductor substrate.

Japanese laid-open patent publications Nos. 2005-094044, 2004-228308,08-078699, and 2004-273483 relate to methods of forming a via hole, athrough hole, and a contact hole. Japanese laid-open patent publicationsNos. 2005-094044 and 2004-228308 disclose that insulation films havingdifferent etching rates are deposited on an upper side of a gateelectrode and on a side surface of the gate electrode to formself-aligning contact. Japanese laid-open patent publication No.08-078699 discloses forming a diffusion layer while using a gateelectrode as a mask. Japanese laid-open patent publication No.2004-273483 discloses an etching method for forming a hole in aninterlayer dielectric. However, these publications fail to teach ordisclose a structure of a through electrode having a small capacity withrespect to a semiconductor substrate and a low resistance, and a methodof manufacturing such a through electrode.

As described above, a conventional through electrode used in athree-dimensional semiconductor device has the following problems: Theresistance of the through electrode is so large that high-speed datatransfer cannot be performed. A deposition time of an embeddedconductive film becomes long because the embedded conductive film of thethrough electrode should have a large film thickness.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above drawbacks. Itis, therefore, an object of the present invention to provide a method ofmanufacturing a through electrode having a low resistance which canshorten an embedding time of a conductive film and can form the throughelectrode with a conductive film having a low resistance, and also asemiconductor device having such a through electrode which can performhigh-speed data transfer.

In order to resolve the above problems, the present invention basicallyadopts the following technology. As a matter of course, the presentinvention covers applied technology in which various changes andmodifications are made therein without departing from the spirit of thepresent invention.

According to one aspect of the present invention, a method ofmanufacturing a through electrode is provided. The method includes thesteps of: while using at least a first conductive film for a gateelectrode as a mask, forming a inner trench for an inner throughelectrode having a columnar semiconductor and a peripheral trench for aperipheral through electrode around an annular semiconductor surroundingthe inner trench; and filling the inner trench and the peripheral trenchwith a through electrode insulation film and a through electrodeconductive film, respectively, to form an inner through electrode and aperipheral through electrode.

In this method, the columnar semiconductor may be provided in the innertrench so that the inner trench is filled with a through electrodeconductive film having a film thickness smaller than that in a case ofno columnar semiconductor.

The method may further include the step of forming a second conductivefilm for the gate electrode on the first conductive film so that aconnecting portion of the inner through electrode is formed by thesecond conductive film while the peripheral through electrode is in afloating state.

The first and second conductive films may be simultaneously patternedwith a gate electrode pattern of a transistor.

A wiring process for the through electrode and a wiring process for thegate electrode may be performed in a same step.

The first conductive film may be made of a material selected from agroup consisting of polysilicon and compounds of refractory metal andsilicon.

The second conductive film may be made of a material selected from agroup consisting of refractory metal, silicides of refractory metal, andnitrides of refractory metal.

The through electrode conductive film may made of a material selectedfrom a group consisting of refractory metal, silicides of refractorymetal, and nitrides of refractory metal.

According to another aspect of the present invention, a semiconductordevice is provided. The semiconductor device includes: an inner trenchfor an inner through electrode having a columnar semiconductor, theinner trench being formed while at least a first conductive film for agate electrode is used as a mask; an peripheral trench for a peripheralthrough electrode formed around an annular semiconductor surrounding thetrench for an inner through electrode, the peripheral trench beingformed while at least a first conductive film for a gate electrode isused as a mask; and an inner through electrode and a peripheral throughelectrode formed by filling the inner trench and the peripheral trenchwith a through electrode insulation film and a through electrodeconductive film, respectively.

In a method of manufacturing a through electrode according to thepresent invention, a first conductive film for a gate electrode isformed as a mask. A second conductive film for the gate electrode isdeposited on the first conductive film and used as a wiring electrode ofa through electrode. Since the through electrode is formed during a gateelectrode formation process, a refractory metal or a compound thereofcan be used to form a through electrode. Accordingly, the throughelectrode can have a low resistance. Further, since a connection wiringprocess of the through electrode and a connection wiring process of thegate electrode are simultaneously performed, a period of time requiredfor the entire process can advantageously be shortened. With such anarrangement, it is possible to provide a through electrode having a lowresistance and a semiconductor device having such a through electrode.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a cross-sectional view showing a three-dimensionalsemiconductor device;

FIG. 2 is a cross-sectional view showing a conventional throughelectrode;

FIG. 3A is a plan view showing a through electrode according to thepresent invention;

FIG. 3B is a cross-sectional view taken along line A-A′;

FIG. 4 is a cross-sectional view showing a process (trench formation)for forming a through electrode according to the present invention;

FIG. 5 is a cross-sectional view showing a process (sidewall insulationfilm deposition) for forming a through electrode according to thepresent invention;

FIG. 6 is a cross-sectional view showing a process (planarization) forforming a through electrode according to the present invention;

FIG. 7 is a cross-sectional view showing a process (mask oxide filmremoval) for forming a through electrode according to the presentinvention;

FIG. 8 is a cross-sectional view showing a process (nitride filmdeposition) for forming a through electrode according to the presentinvention;

FIG. 9 is a cross-sectional view showing a process (gate patterning) forforming a through electrode according to the present invention;

FIG. 10 is a cross-sectional view showing a process (nitride filmdeposition) for forming a through electrode according to the presentinvention;

FIG. 11 is a cross-sectional view showing a process (wiring formation)for forming a through electrode according to the present invention;

FIG. 12 is a cross-sectional view showing a process (rear grinding) forforming a through electrode according to the present invention;

FIG. 13 is a cross-sectional view showing a process (rear insulationfilm opening) for forming a through electrode according to the presentinvention;

FIG. 14 is a cross-sectional view showing a process (bump formation) forforming a through electrode according to the present invention; and

FIG. 15 is a cross-sectional view showing a three-dimensionalsemiconductor device according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the present invention will be described withreference to FIGS. 3A and 3B. FIGS. 3A and 3B show a structure of athrough electrode according to the present invention. FIG. 3A is a planview showing the structure of the through electrode, and FIG. 3B is across-sectional view taken along line A-A′ of FIG. 3A.

The through electrode of the present invention has a double throughelectrode structure including an inner through electrode 12 and aperipheral through electrode 14 in a semiconductor substrate 11. Theperipheral through electrode 14 is formed like a ring in thesemiconductor substrate 11. An annular semiconductor 11 a is formedinside of the peripheral through electrode 14. The inner throughelectrode 12 is formed so as to be surrounded by the annularsemiconductor 11 a. The inner through electrode 12 serves as an actualthrough electrode. No potential is supplied to the peripheral throughelectrode 14 and the annular semiconductor 11 a, which are in a floatingstate. Thus, the peripheral through electrode 14 and the annularsemiconductor 11 a are provided in order to reduce a capacity betweenthe semiconductor substrate 11 and the inner through electrode 12. Theinner through electrode 12 and the peripheral through electrode 14 areformed within a trench defined in the semiconductor substrate 11. Eachof the inner through electrode 12 and the peripheral through electrode14 has a through electrode insulation film for insulation fromsurrounding semiconductors and a through electrode conductive filmsurrounded by the insulation film.

The peripheral through electrode 14 is formed within an annular trenchdefined between the semiconductor substrate 11 and the annularsemiconductor 11 a. The peripheral through electrode 14 has peripheralthrough insulation films 15 for insulation from the semiconductorsubstrate 11 and the annular semiconductor 11 a, and a peripheralthrough conductive film 14 a inside of the peripheral through insulationfilms 15. The inner through electrode 12 is formed within a trenchdefined in the annular semiconductor 11 a. A plurality of columnarsemiconductors (columnar semiconductor portions) 11 d are formed withina trench for an inner through electrode. The inner through electrode 12has inner through insulation films 13 between the columnarsemiconductors 11 d and the annular semiconductor 11 a and betweenadjacent columnar semiconductors 11 d, and an inner through conductivefilm 12 a.

The inner through electrode 12 is formed between the annularsemiconductor 11 a and the columnar semiconductors 11 d. The columnarsemiconductors 11 d are spaced from the annular semiconductor 11 a atequal intervals and located so as to have equal intervals betweenadjacent columnar semiconductors 11 d. These intervals allow theinsulation films and the conductive film of the inner through electrodeto be deposited so as to be filled equally into between the columnarsemiconductors with a small film thickness. In order to fully fill afilm into a trench, the film is required to have a film thickness largerthan a half of a diameter of the trench. The inner area of the innerthrough electrode is divided by the columnar semiconductors arranged atequal intervals. By reducing the equal intervals of the columnarsemiconductors, the required film thickness to be deposited can bereduced. Further, the film can uniformly be filled by arranging thecolumnar semiconductors at the equal intervals.

For example, in FIG. 3A, square columnar semiconductors are arrangedwith four rows and four columns. It is assumed that an outer square hasa width of 30 μm and each columnar semiconductor within the outer squarehas a width of 2 μm. When the insulation film has a thickness of 0.1 μm,the inner through electrode can be filled with a conductive film havinga thickness of about 2 μm. If the inner through electrode is not dividedby columnar semiconductors, then it is necessary to fill a conductivefilm having a film thickness of at least 15 μm, which is a half of thewidth of the outer square (30 μm). The divided inner through electrodeneeds only one seventh of the film thickness required in a case wherethe inner through electrode is not divided by columnar semiconductors.Thus, the inner through electrode can be filled with a film having asmall film thickness. Accordingly, a period of time required forembedding a conductive film in a manufacturing process can be reduced,and loads on a production line can also be reduced. Further, it ispossible to obtain uniform quality of the film because of a small filmthickness. Accordingly, it is possible to obtain an inner throughelectrode having a low resistance.

Further, it is desirable that each of the columnar semiconductors 11 dis in the form of a square or a rectangle because the columnarsemiconductors 11 d are arranged at equal intervals. However, the shapeof the columnar semiconductors 11 d is not limited to specific ones, andthe columnar semiconductors 11 d may have any shape as long as thecolumnar semiconductors are arranged substantially at equal intervals sothat a conductive film can uniformly be filled into spaces between thecolumnar semiconductors. Further, only one columnar semiconductor may bedisposed, or a plurality of columnar semiconductors may be disposed. Byreducing the size of the columnar semiconductors, an area in which thecolumnar semiconductors are formed is reduced so as to increase a ratioof an area in which the conductive film is formed. Accordingly, it ispossible to obtain an inner through electrode having a lower resistance.The resistance of the through electrode varies according to the shapesof the inner through electrode 12 and the columnar semiconductors 11 d.Therefore, the shapes of the inner through electrode 12 and the columnarsemiconductors 11 d can be changed depending on a resistance or acapacity required for a through electrode.

The peripheral through electrode 14 is insulated and isolated from theannular semiconductor 11 a and the semiconductor substrate 11,respectively, by the peripheral through electrode insulation films 15.The peripheral through electrode 14 and the annular semiconductor 11 aare not connected to any potential wiring line and are thus in afloating state. Since the peripheral through electrode 14 is in afloating state, it does not serve as an electrode. Accordingly, theperipheral through conductive film 14 a may be eliminated so that theperipheral through electrode 14 is formed by one peripheral. throughelectrode insulation film 15. Thus, a space between the semiconductorsubstrate 11 and the annular semiconductor 11 a, in which the peripheralthrough electrode 14 is formed, can be made equal to or smaller than theintervals between the columnar semiconductors 11 d. Further, the annularsemiconductor 11 a and the peripheral through electrode 14 may bedoubted.

Further, since the peripheral through electrode 14 and the annularsemiconductor 11 a are in a floating state, it is possible todramatically reduce a capacity between the semiconductor substrate 11and the inner through electrode 12. The capacity between thesemiconductor substrate 11 and the inner through electrode 12 is asynthesis capacity of series connection of a capacity between thesemiconductor substrate 11 and the peripheral through electrode 14, acapacity between the peripheral through electrode 14 and the annularsemiconductor 11 a, and a capacity between the annular semiconductor 11a and the inner through electrode 12. Accordingly, the capacity betweenthe semiconductor substrate 11 and the inner through electrode 12 isdramatically reduced. Furthermore, reduction of the capacity between theinner through electrode 12 and the semiconductor substrate 11 eliminateslimitation on the film thickness of an insulation film. For the filmthickness of the inner through electrode insulation films 13 and theperipheral through electrode insulation films 15, only a withstandvoltage should be considered. Accordingly, the film thickness of theinner through electrode insulation films 13 and the peripheral throughelectrode insulation films 15 can remarkably be reduced as compared tothe film thickness of conventional insulation films. For example, thefilm thickness can be as small as not more than one third of the filmthickness of the conventional insulation films.

A through electrode according to the present invention includes an innerthrough electrode in which columnar semiconductors are provided, anannular semiconductor, and a peripheral through electrode. Trenches aredefined in the semiconductor substrate 11 to form the annularsemiconductor 11 a and the columnar semiconductors 11 d. Since thecolumnar semiconductors 11 d are provided, these trenches have a finerpattern as compared to trenches formed in a conventional throughelectrode formation process. Accordingly, it is desirable to form thethrough electrodes at the earliest possible timing before a wiringprocess.

Generally, through electrodes are formed during a wiring process orafter a wiring process. However, in the case where through electrodesare formed after a wiring process, a variety of interlayer dielectricsare used in a space to a semiconductor substrate. The film thickness ofthe interlayer dielectrics is also large. When a various types ofinsulation films are etched simultaneously, a normal etching profile isunlikely to be obtained because the respective insulation films havedifferent etching rates. Accordingly, a fine pattern cannot be obtained,and a large pattern is formed. If the formed pattern has large intervalsbetween columnar semiconductors, the through electrode insulation filmsand the through electrode conductive films should have a large filmthickness. Therefore, it is desirable to form the through electrodes inthe earliest possible step.

A manufacturing process will briefly be described below. After anisolation process, trenches are formed for a peripheral throughelectrode and an inner through electrode. Insulation films andconductive films are deposited so as to form inner through electrodeinsulation films 13, peripheral through insulation films 15, an innerthrough electrode conductive film 12 a, and a peripheral throughelectrode conductive film 14 a. Then, a planarization process isperformed. Polysilicon is used for the conductive film becausepolysilicon can cope with a high-temperature treatment in a welldiffusion or the like. If metal is used for the conductive film, it isnecessary to limit a high-temperature treatment and form a protectivefilm against contamination. Thus, metal cannot be used because itbecomes necessary to change conditions of a standard semiconductorprocess.

Then, a diffusion layer, transistors, interconnections 16, and the likeare formed by a usual diffusion process. Interconnections for a throughelectrode are simultaneously formed during the wiring process. Aftercompletion of the wiring process, a rear face of the semiconductorsubstrate is ground until the semiconductor substrate is thinned so asto have a predetermined thickness. An insulation film 18 for protectingthe semiconductor device is formed on the rear face of the semiconductorsubstrate. Further, an opening is formed in the insulation film 18 at aportion corresponding to the inner through conductive film 12 a. A bump19 is formed in the opening and connected to an exterior of thesemiconductor device. In FIG. 3B, the bump 19 is formed on the rear faceof the semiconductor substrate 11. Similarly, an opening may be formedin the insulation film 17, and a bump 19 may be formed on the front faceof the semiconductor substrate 11. In this manner, a through electrodeaccording to the present invention is manufactured.

A through electrode according to the present invention has an innerthrough electrode, and an annular semiconductor and a peripheral throughelectrode in a floating state around the inner through electrode. Theinner through electrode includes columnar semiconductors arrangedtherein at equal intervals. The inner through electrode can have a lowresistance by using a conductive thin film having a small thickness.Since the annular semiconductor and the peripheral through electrode areprovided so as to be in a floating state, the capacity between thesemiconductor substrate and the inner through electrode can bedramatically reduced. With such an arrangement, it is possible toprovide a through electrode which has a low resistance and a smallcapacity and is easy to manufacture. Further, a semiconductor devicewhich can perform high-speed data transfer can be provided withprovision of this through electrode.

An example of a manufacturing method of a through electrode according tothe present invention will be descried below with reference to FIGS. 4through 15. The following manufacturing method of a through electrodecan be applied to a standard semiconductor process without changing thestandard semiconductor process to a large extent. In the followingexample, a through electrode is formed during a gate electrode formationprocess. FIGS. 4 through 15 are cross-sectional views of a semiconductordevice according to a manufacturing process of a through electrode. InFIGS. 4 through 10, a cross-sectional view of one through electrode isillustrated on the left side of each drawing, and a cross-sectional viewof a transistor is illustrated on the right side of each drawing. FIGS.11 through 15 are cross-sectional views of one through electrode.

As shown in FIG. 4, a shallow trench isolation (STI) insulation film 22for device isolation is formed on a semiconductor substrate 21. Further,a well diffusion layer (not shown) is formed, and then a gate insulationfilm and a gate polysilicon 23 as a first conductive film for a gateelectrode are deposited thereon. These steps are the same as those in ausual process. The same process is performed on an area in which athrough electrode is to be formed and on an area in which a transistoris to be formed. Further, a mask oxide film 24 for etching mask isdeposited thereon. In order to form a through electrode, trenches 27 foran inner through electrode 25 and a trench 28 for a peripheral throughelectrode 26 are formed by lithography and etching technology. Thetrenches 27 and 28 for inner and peripheral through electrodes dividethe silicon substrate 21 into an annular semiconductor 30 and columnarsemiconductors 29.

The trenches 27 for an inner through electrode are designed so as tohave the same width. The trench 28 for a peripheral through electrode isdesigned so as to have a width equal to or smaller than that of thetrenches 27 for an inner through electrode. Since the trenches 27 for aninner through electrode have the same width, the trenches 27 can befilled uniformly with a conductive film having the same film thickness.At that time, the trench 28 can also be filled with a conductive film.In this case, patterning is not conducted on a transistor portion shownon the right side of FIG. 4. The gate polysilicon 23 may be made of anymaterial used as a first conductive film for a gate electrode. Insteadof polysilicon, silicide containing refractory metal can be used for thegate polysilicon 23.

Subsequently, as shown in FIG. 5, a sidewall insulation film 31 isdeposited on the overall surface of the semiconductor substrate 21. Theinsulation film formed on the overall surface of the silicon substrateincludes inner through electrode insulation films 32 formed in thetrenches 27 for an inner through electrode 25 and a peripheral throughelectrode insulation film 33 formed in the trench 28 for a peripheralthrough electrode 26. The inner through electrode insulation films 32serve to insulate columnar semiconductors from an annular semiconductorand insulate adjacent columnar semiconductors from each other. Theperipheral through electrode insulation film 33 serves to isolate theannular semiconductor from the semiconductor substrate.

As shown in FIG. 6, a conductive film is deposited on the overallsurface of the semiconductor substrate 21 by using a CVD method. Thus,the trenches 27 for an inner through electrode 25 and the trench 28 fora peripheral through electrode 26 are filled with the conductive film.In this case, since the trenches 27 are divided at equal intervals bythe columnar semiconductors 29, the trenches 27 can be filled with aconductive film having a small film thickness. The conductive film canhave uniform quality and a low resistance with a small film thickness.The conductive film is formed on the overall silicon substrate. Theconductive film includes an inner through conductive film 34 formed inthe trenches 27 for an inner through electrode 25 and a peripheralthrough conductive film 35 formed in the trench 28 for a peripheralthrough electrode.

Then, a planarization process is performed so as to form an innerthrough electrode 25 and a peripheral through electrode 26 in thetrenches. Materials for the conductive film include refractory metalssuch as tungsten and titanium, silicides of the refractory metals, andnitrides of the refractory metals. In this case, a CVD method, asputtering method, or the like may be used as a deposition method. Sinceno potential is supplied to the peripheral through electrode 26 and usedin a floating state, the trench 28 for the peripheral through electrode26 may be made small in size and fully filled with an insulation filmwithout a conductive film formed therein.

Next, as shown in FIG. 7, the sidewall insulation film 31 and the maskoxide film 24 are removed so as to expose the gate polysilicon 23. Thesteps from deposition of the mask oxide film 24 to removal of the maskoxide film 24 are dedicated to a through electrode. As shown in FIG. 8,a gate electrode metal 36 and a nitride film 37 are deposited on thegate polysilicon 23. Materials for the gate electrode metal includerefractory metals such as tungsten and titanium, silicides of therefractory metals, and nitrides of the refractory metals. Alternatively,these materials may be combined to form a plurality of layers in thegate electrode metal.

As shown in FIG. 9, patterning of a gate electrode is conducted. In thegate patterning, a gate electrode 38 is formed at a transistor portionon the right side of FIG. 9, and connecting portions 39 and 40 for theinner through electrode 25 and the peripheral through electrode 26 aresimultaneously formed. Further, a nitride film 41 is deposited thereon(FIG. 10). The nitride film 41 serves to protect the gate electrode forself-aligning contact. Formation of a nitride film is a standardsemiconductor process for dynamic random access memories. By coveringthe through electrode with the nitride film 41, it is also possible toprevent contamination by metals from a second conductive film for thegate electrode and the through electrode.

The deposition of the gate electrode metal 36 and the nitride film 37,the lithography and etching for the gate electrode, and the depositionof the nitride film 41 are not specific to a through electrode and canalso be used as a standard semiconductor process. Thereafter, a usualsemiconductor process is performed. The connecting portions 39 and 40for the inner through electrode 25 and the peripheral through electrode26 include a gate polysilicon 23, a gate electrode metal 36, and anitride film 37 as with a gate electrode of a usual transistor.Accordingly, the through electrode can be processed in the same manneras the gate electrode.

As described above, the through electrode is formed while the firstconductive film for the gate electrode is used as a mask. Sincerefractory metals and compounds thereof can be employed for theconductive film of the through electrode, the resistance of the throughelectrode can be reduced to a low value. Further, the second conductivefilm for the gate electrode can be employed for the connecting portionsof the through electrode. Furthermore, steps after the deposition of thesecond conductive film for the gate electrode, which include the gatepatterning process and the patterning process of the connecting portionsof the through electrode, are also performed in a standard semiconductorprocess. Thus, the same processes can be used. Accordingly, the surfaceof the through electrode has the same structure as the gate electrode.The number of steps dedicated to formation of the through electrode canbe made small because the aforementioned steps can also be used for astandard semiconductor process. Thus, the method according to thepresent invention is advantageous in mass production.

Then, an interlayer film 42 are formed, and interconnections 43 areformed in the interlayer film 42 (FIG. 11). Thus, a diffusion and wiringprocess of a semiconductor device is completed. The following steps arespecific to a through electrode. As shown in FIG. 12, a rear face of thesemiconductor substrate 21 is ground until the semiconductor substrate21 is thinned so as to have a predetermined thickness. Specifically, therear face of the semiconductor substrate 21 is ground and thinned untilthe inner through electrode 25 and the peripheral through electrode 26are exposed. Grinding of the rear face of the semiconductor substrate 21may be conducted halfway, and then secondary polishing such as wetpolishing or dry polishing may be conducted. An insulation film 44 isdeposited on the rear face of the semiconductor substrate 21, and a holefor a bump is formed in the insulation film 44 (FIG. 13). Then, a bump45 is formed in the hole (FIG. 14). If a bump is formed on the frontface of the substrate, a hole for a bump is formed in the interlayerfilm 42 and a bump is formed on the interconnections 43. Bumps may beformed on the front and rear faces of the substrate. Thereafter, thesemiconductor substrate 21 is divided into chips having a semiconductordevice with a through electrode.

FIG. 15 shows a three-dimensional semiconductor device having twostacked semiconductor devices. A front face of an upper semiconductordevice, in which transistors and interconnections are formed, isprotected by a protective layer. The upper semiconductor device isconnected to a lower semiconductor device via a bump formed on a rearface thereof. A rear face of the lower semiconductor device is protectedby an insulation film. The upper semiconductor device is connected tothe upper semiconductor device via a bump formed on a front facethereof. In order to maintain the reliability and electriccharacteristics of the upper semiconductor device and the lowersemiconductor device, it is desirable to seal a space between the upperand lower semiconductor devices by an adhesive layer 46 made of resin.Thus, by stacking semiconductor devices each having a through electrode,it is possible to produce a small-sized three-dimensional semiconductordevice.

According to a method of manufacturing a through electrode in thepresent example, a through electrode is formed while a first conductivefilm for a gate electrode is used as a mask. A refractory metal or acompound thereof, which is used for the gate electrode, can be used toform a through electrode. Accordingly, the through electrode can have alow resistance. Further, the through electrode can be protectedsimultaneously by a nitride film for covering the gate electrode,Therefore, it is possible to prevent contamination. Thus, themanufacturing method according to the present invention can be appliedto a usual semiconductor process with common steps. With such commonsteps, it is possible to reduce the number of steps dedicated toformation of a through electrode, shorten a required process time, anduse common mass production facilities.

Further, a through electrode according to the present invention has aninner through electrode, and a peripheral through electrode and anannular semiconductor in a floating state around the inner throughelectrode. The inner through electrode includes columnar semiconductorsarranged therein at equal intervals. The inner through electrode can beformed by using a conductive thin film having a small thickness. Sincethe annular semiconductor and the peripheral through electrode areprovided so as to be in a floating state, the capacity between thesemiconductor substrate and the inner through electrode can bedramatically reduced. With such an arrangement and manufacturing methodof the through electrode, it is possible to provide a through electrodewhich has a low resistance and a small capacity and is easy tomanufacture. Further, a semiconductor device which can performhigh-speed data transfer can be provided with provision of this throughelectrode.

Although certain preferred embodiment and example of the presentinvention have been shown and described in detail, the present inventionis not limited to the illustrated examples. It should be understood thatvarious changes and modifications may be made therein without departingfrom the scope of the appended claims. Further, the illustrated examplesinclude inventions at various stages, and thus various inventions can beextracted from proper combinations of the disclosed elements orprocesses. For example, inventions can be extracted from this disclosureas long as desired effects can be achieved even if some of the disclosedelements or processes are eliminated.

1. A semiconductor device comprising: an inner trench for an innerthrough electrode formed in a semiconductor substrate and having acolumnar semiconductor, said inner trench being formed while at least afirst conductive film formed on said semiconductor substrate for a gateelectrode is used as a mask; a peripheral trench for a peripheralthrough electrode formed on the semiconductor substrate around anannular semiconductor surrounding said inner trench for said innerthrough electrode, said peripheral trench being formed while at leastthe first conductive film for the gate electrode is used as the mask;and said inner through electrode and said peripheral through electrodeformed by etching said first conductive film and filling said innertrench and said peripheral trench with a through electrode insulationfilm and a through electrode conductive film, respectively.
 2. Thesemiconductor device claimed in claim 1, wherein said columnarsemiconductor is provided in said inner through electrode.
 3. Thesemiconductor device claimed in claim 2, further comprising: a secondconductive film for the gate electrode, said second conductive filmbeing formed on said first conductive film, wherein a connecting portionof said inner through electrode is formed by said second conductive filmwhile said peripheral through electrode is in a floating state.
 4. Thesemiconductor device claimed in claim 3, wherein said first conductivefilm comprises at least one of polysilicon and compounds comprisingrefractory metal and silicon.
 5. The semiconductor device claimed inclaim 3, wherein said second conductive film comprises at least one ofrefractory metal, silicides comprising refractory metal, and nitridescomprising refractory metal.
 6. The semiconductor device claimed inclaim 3, wherein said through electrode conductive film comprises atleast one of refractory metal, silicides comprising refractory metal,and nitrides comprising refractory metal.
 7. The semiconductor deviceclaimed in claim 1, wherein said peripheral through electrode and saidannular semiconductor are in a floating state in which no potential issupplied.
 8. The semiconductor device claimed in claim 1, wherein saidcolumnar semiconductor has one of a square and a rectangular shapespaced from said annular semiconductor at equal intervals, and whereinsaid inner through conductive film is filled into the equal intervals.9. The semiconductor device claimed in claim 1, wherein said columnarsemiconductor comprises a plurality of columnar semiconductor portionshaving one of a square and a rectangular shape, wherein said pluralityof columnar semiconductor portions are spaced from said annularsemiconductor and an adjacent columnar semiconductor portion at equalintervals, and wherein said inner through conductive film is filled intothe equal intervals.
 10. The semiconductor device claimed in claim 1,further comprising: a plurality of peripheral layers outside of saidperipheral through electrode, said plurality of peripheral layerscomprising an additional annular semiconductor and an additionalperipheral through electrode.
 11. A semiconductor device comprising: athrough electrode, comprising: at least one columnar semiconductorplaced within an inner trench with a gap left between the at least onecolumnar semiconductor and sides of the inner trench; an inner throughelectrode embedded within the gap; a through electrode insulation filmbeing formed in the inner trench; a peripheral through electrodeembedded within an outer trench surrounding said inner throughelectrode; and a through electrode conductive film being formed in theouter trench.
 12. The semiconductor device as claimed in claim 11,further comprising: a ring-shaped semiconductor which surrounds theinner through electrode and which is placed between the inner throughelectrode and the peripheral through electrode.
 13. The semiconductordevice as claimed in claim 12, wherein the peripheral through electrodeand the ring-shaped semiconductor are supplied with no electricpotential and are kept in an electric floating state.
 14. Thesemiconductor device as claimed in claim 11, wherein the at least onecolumnar semiconductor has one of a square shape and a rectangular shapeto define a substantially uniform gap between the at least one columnarsemiconductor and the peripheral through electrode.
 15. Thesemiconductor device as claimed in claim 11, wherein a plurality ofcolumnar semiconductors comprising the at least one columnarsemiconductor are arranged within the inner trench in a matrix manner.16. The semiconductor device as claimed in claim 15, further comprising:a ring-shaped semiconductor which surrounds the inner through electrodeand which is placed between the inner through electrode and theperipheral through electrode.
 17. The semiconductor device as claimed inclaim 16, wherein said through electrode insulation film comprises: aninsulating layer interposed between the inner through electrode and theplurality of columnar semiconductors; and another insulating layerinterposed between the inner through electrode and the ring-shapedsemiconductor.
 18. The semiconductor device as claimed in claim 16,wherein said through electrode insulation film comprises an outerinsulating layer interposed between the ring-shaped semiconductor andthe peripheral through electrode.
 19. The semiconductor device claimedin claim 11, wherein said inner and the peripheral through electrodescomprise at least one of polysilicon and compounds comprising refractorymetal and silicon.
 20. A semiconductor device comprising: a throughelectrode, comprising: a semiconductor device which comprises pluralsemiconductor devices, said plural semiconductor devices being stuck oneach other; a set of semiconductor pillars, the semiconductor pillarsbeing arranged adjacently to one another to form a first gap thereamong;a semiconductor ring formed to surround the set of semiconductor pillarsto form a second gap therebetween; a first conductive material formed tofill the first and second gaps; and a second conductive material formedto surround the semiconductor ring, wherein at least one of said pluralsemiconductor devices comprises the semiconductor device claimed inclaim
 11. 21. The device as claimed in claim 20, wherein thesemiconductor ring and the second conductive material are in anelectrical floating state.
 22. The device as claimed in claim 21,further comprising: a first insulating film intervening between the setof semiconductor pillars and the first conductive material; a secondinsulating film intervening between the first conductive material andthe semiconductor ring; and a third insulating film intervening betweenthe semiconductor ring and the second conductive material.
 23. Thedevice as claimed in claim 21, wherein the set of semiconductor pillarsis arranged in a matrix form including a plurality of rows and columns.24. A semiconductor device, comprising: a through electrode, comprising:a set of semiconductor pillars formed in an inner trench, thesemiconductor pillars being arranged adjacently to one another to form afirst gap thereamong; a through electrode insulation film being formedin the inner trench; a semiconductor ring formed to surround the set ofsemiconductor pillars to form a second gap therebetween; a firstconductive material formed to fill the first and second gaps; a secondconductive material formed in an outer trench to surround thesemiconductor ring; and a through electrode conductive film being formedin the outer trench.
 25. The device as claimed in claim 24, wherein thesemiconductor ring and the second conductive material are in anelectrical floating state.
 26. The device as claimed in claim 25,wherein the set of semiconductor pillars is arranged in a matrix formincluding a plurality of rows and columns.
 27. The device as claimed inclaim 24, further comprising: a first insulating film interveningbetween the set of semiconductor pillars and the first conductivematerial; a second insulating film intervening between the firstconductive material and the semiconductor ring; and a third insulatingfilm intervening between the semiconductor ring and second conductivematerial.